Patient infusion media warmer and method of use

ABSTRACT

A warming unit and method for warming an infusion medium prior to introducing the medium into a patient&#39;s body. The apparatus includes an outer casing, inlet and outlet tubes secured to the outer casing, a fluid conduit for transporting the infusion medium through the warming unit, and a heating element disposed proximate to the fluid conduit for warming the infusion medium flowing therethrough. The warming unit can form part of a system, which further includes a controller for controlling various functions of and separate from the warming unit, a reservoir containing the infusion medium, and a power source for powering the warming unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/501,238, filed Aug. 9, 2006, which claims the benefit of U.S.Provisional Application No. 60/707,182, filed Aug. 11, 2005, U.S.Provisional Application No. 60/773,336, filed Feb. 15, 2006, and U.S.Provisional Application No. 60/773,314, filed Feb. 15, 2006, each ofwhich is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a warming unit for warming a fluidflowing therethrough, and, in particular, to a warming unit for warminga patient infusion medium being infused into a patient. The warming unitforms part of a system for warming a patient infusion medium including,for example, a controller for controlling and monitoring variouscharacteristics of the warming unit and a power unit for powering thesystem.

2. Description of Related Art

Warming systems for warming a patient infusion medium (interchangeablyreferred to as “medium”) for infusion into a patient via an infusiontube, indirectly or directly, are known in the art. Some such systems,for example, may typically use a coiled length of tube to minimize thearea necessary for contact with or placement in close proximity to anindirect heating element. Other systems use a heating element integratedwith tubing, such as a braided heating element disposed between innerand outer layers of a dual extruded tube. Prior art warming systems alsotypically provide for measuring the temperature of the medium at somepoint within the system, and include a control unit integral with theheating element. Such control unit generally controls power to theheating element and measures the output temperature of the medium.

However, the warming systems of the prior art suffer from drawbacks andproblems. One such problem is that the warming systems tend to be bulkyand un-ergonomic, which leads to patient discomfort when the warmingsystem is secured to the body of the patient.

A second problem with prior art warming systems is that they are proneto leakage. One source of leakage typically is the location at which aconnector, or luer, at an end of the heating systems attaches to amating connector of a neighboring piece of tubing. A second source oftypical leakage is heating element overheating, which, for example, maycreate a hole in the tubing. This problem is compounded in those heatingsystems having onboard circuitry: once the infusion medium passesthrough the hole in the tubing, the escaped medium may contact thecircuitry, and, in some cases, the heating system may short, smoke,and/or catch fire. As a result, a safety hazard can occur, the patientmay be placed in discomfort or danger, and the heating system may needto be replaced. Further, any medical procedure underway might also needto be suspended while the heating system is replaced.

SUMMARY OF THE INVENTION

The present invention solves these problems, as well as others, byproviding a warming unit and system for warming a patient infusionmedium, wherein the warming unit includes an ergonomic design that iscomfortably securable to a patient or easily attachable to anotherlocation, and provides an efficient warming operation, a low risk ofleakage, and an improved flowrate over the medium warmers of the priorart. Embodiments of the present invention include separate controlelectronics from the warming unit, thereby reducing or eliminatingproblems associated with prior art integrated systems.

According to one embodiment of the present invention, the warming unitincludes an outer casing, a laminated heating assembly, one or moresensors, and inlet and outlet tubes. The warming unit optionallyincludes a connector port for connecting the fluid warmer to acontroller, which controls various functions of the fluid warmer. Afluid conduit is formed within the casing, and, according to oneembodiment, the fluid conduit defines a serpentine or meandering path,prolonging a time period during which a medium passing through thewarming unit is in contact with, or in close proximity to, the laminatedheating assembly. Among other advantages, the conduit of someembodiments of the present invention reduces formation of air bubbles inthe medium to be conducted, by sizing and/or shaping the cross-sectionalarea of the conduit such that bubble formation has a low likelihood ofoccurrence.

According to one embodiment, the laminated heating assembly includes aheating element disposed on a plate, which is sandwiched between firstand second insulating sheets. The laminated heating assembly may alsoinclude one or more sensors for measuring the temperature of the heatingelement or the medium flowing through the warming unit, for example.Examples of sensors applicable to the present invention include, but arenot limited to, thermocouples, thermistors, resistor elements, and anyother suitable device for measuring and/or otherwise determiningtemperature. According to a further embodiment of the present invention,the heating element is located proximate to the fluid conduit and alignswith and extends along the fluid conduit in a parallel manner, althoughit is within the scope of the present invention that the heating elementis in the form of other shapes and configurations.

The laminated heating assembly is provided within the outer casing, forexample, by being enclosed between first and second portions of theouter casing. Further, the warming unit optionally includes a pluralityof extensions and corresponding openings formed on the first and secondcasing portions, respectively, to align and secure the casing portionstogether. The warming unit optionally also includes a seal disposedbetween the first and second casing portions. The seal is seated, forexample, within a groove formed in one of the first and second casingportions. The first and second casing portions may be secured togetherby ultrasonic welding, gluing, or any other suitable method ofattachment. In some embodiments, once assembled together, the first andsecond casing portions are permanently secured to each other. As aresult, the warming unit has improved leakage and tamper resistance. Insome variations, the warming unit is intended to be disposed after asingle use.

In embodiments of the present invention, the warming unit includes aconnector portion formed on, for example, or otherwise attached to, thelaminated heating assembly. The connector portion includes one or morecontact points to provide power to the heating element and to transmitsignals with the one or more sensors and/or other features of the unit.The contact points are coupled, for example, to the heating element, tothe one or more sensors, and/or to other features via circuit pathsformed on the laminated heating assembly or via wires or othercouplings. Wires or other couplings connected to the connector portion,in turn couple the warming unit to the controller and/or a power source.In some embodiments, the power source may be attached and detached fromthe connector portion, allowing flexibility in portability of thewarming unit and the use of a variety of power sources (e.g., any powersource meeting the power requirements may be connected via the connectorportion, so long as suitable connection mechanism is provided). Otherfeatures optionally included with the warming unit include a flowratemeasurement device to measure a flowrate of a medium passing through thewarming unit or otherwise delivered to a patient.

In some embodiments, external control circuitry for controlling thetemperature of the medium flowing through the warming unit is containedin a controller. Consequently, the circuitry is not susceptible toshorting, smoking, or catching fire, for example, as a result of escapedmedium from the heating unit coming into contact with the controlcircuitry. The warming unit of the present invention thereby providesimproved patient and caregiver safety and reliability over prior artwarmers having integrated control circuitry.

In some embodiments, the warming unit forms a portion of or is otherwiseusable with an infusion medium warming system, which further includes,for example, a power supply, a separate controller, and a reservoir fora medium to be warmed. In some embodiments, the controller providespower or controls power delivery to, and transmits and receives data,such as inlet and outlet temperature data, with the warming unit. Thecontroller may also receive and display a temperature of the heatingelement of the warming unit or display or receive input of otherinformation. Display may include, for example, such information as avisual alarm or the temperature of the medium flowing through thewarming unit (e.g., inlet and/or outlet temperature). Additionally, thecontroller may also include an audible and/or visual alarm, for example,which is triggered when the monitored temperature exceeds apredetermined value, or when another alarm condition exists.

Additional advantages and novel features of the invention will bepartially set forth in the description that follows, and will alsobecome apparent to those skilled in the art upon examination of thefollowing or upon learning by practice of the invention.

BRIEF DESCRIPTION OF DRAWINGS

Other aspects of the present invention will be better understood fromthe following description, along with the accompanying drawings,wherein:

FIG. 1 shows an infusion medium warming system, including a mediumreservoir, a warming unit, a controller for monitoring and controllingthe warming unit, and a power supply, in accordance with an embodimentof the present invention;

FIG. 2 shows an exploded view of the warming unit according to anembodiment of the present invention;

FIG. 3 shows another exploded view of the warming unit of FIG. 2;

FIG. 4A is a perspective view of a central portion of the warming unit,in accordance with an embodiment of the present invention;

FIG. 4B is a cross-sectional view of a first variation of the warmingunit of FIG. 4A;

FIG. 4C is a cross-sectional view of a second variation of the warmingunit of FIG. 4A;

FIG. 5 is another perspective view of the warming unit of FIG. 4;

FIG. 6 shows an embodiment of the warming unit having variousintravenous fittings included therewith; and

FIG. 7 is a side view of a warming unit according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

The present invention relates to an improved warming unit for warming apatient infusion medium, such as prior to introducing the medium into apatient's body. Referring to FIG. 1, in one embodiment, the warming unit10 forms part of an infusion medium warming system, which furtherincludes a power supply 20, a controller 30, a reservoir 35 connected tothe warming unit 10, and a coupling 40 extending between the controller30 and the warming unit 10. In the embodiment of FIG. 1, the controller30 controls power delivery to, transmits data to, and receives data fromthe warming unit 10, such as temperature data.

The controller 30 includes, for example, a display for displayinginformation, such as a visual alarm, and/or a temperature of the mediumflowing through the warming unit 10 (e.g., inlet and/or outlettemperature). According to one embodiment, the controller 30 receivesand displays a temperature of a heating element (described furtherbelow) of the warming unit 10. According to one embodiment, thecontroller 30 further includes an audible and/or visual alarm that istriggered when, for example, a monitored temperature exceeds apredetermined value or when another alarm condition exists.

The power supply 20 provides a regulated voltage to the controller 30and/or to the warming unit 10. Although illustrated as two separatecomponents, the power supply 20 may also be integral with the controller30.

Referring to FIGS. 2 and 3, according to one embodiment of the presentinvention, the warming unit 10 includes outer casing portions 110, 120,a laminated heating assembly 50, first and second sensors 60 and 70, aconnector port 80, an inlet tube 90, and an outlet tube 100.

The first casing portion 110 and second casing portion 120, uponassembly, form a single enclosing casing (see assembled casing 45 ofFIGS. 4 and 5). In one embodiment, the first and second casing portions110, 120 are formed from a polymeric material using an injection moldingprocess, although it is within the scope of the present invention to useany suitable material and any suitable method to form the casingportions 110, 120. An inner surface of the first casing portion 110 mayinclude a plurality of extensions 130 distributed along a perimeterthereof. The extensions 130 engage corresponding openings 140 formed inthe second casing portion 120, for example. The extensions 130 and thecorresponding openings 140 perform a positioning and union function toalign and connect the first and second casing portions 110, 120, uponassembly. However, it is within the scope of the invention to includealternate structure, such as a raised ridge and corresponding matinggroove or other features to align and connect the first and secondcasing portions 110, 120. In one embodiment, the extensions 130 and thecorresponding openings 140 are integrally formed in the respective firstand second casing portions 110, 120.

Referring to FIG. 3, in one embodiment, the inner surface of the firstcasing portion 110 further includes a recess 150 for retaining thelaminated heating assembly 50 therein. According to one embodiment, thedepth of the recess 150 matches the thickness of the laminated heatingassembly 50 so that, when the laminated heating assembly 50 is insertedinto the recess 150, a surface thereof, opposite the first casingportion 110, is approximately flush with a raised edge portion 160 ofthe first casing portion 110 surrounding the recess 150. Therefore, oncethe warming unit 10 is assembled, adjacent inner faces of the first andsecond casing portion 110, 120 abut each other without forming a gap orby formulating a minimal gap therebetween.

According to one embodiment, the warming unit 10 also includes a seal,which seats into the groove 165 formed in the first casing portion 110along the perimeter of the recess 150. The seal, such as an o-ring orgasket, provides the casing 45 with a seal at the interface between thefirst and second casing portions 110, 120. In some embodiments, onceassembled, the first and second casing portions 110, 120 are permanentlysecured to each other, such as by ultrasonic welding, gluing, or anyother suitable method of attachment.

Control circuitry for controlling a temperature of the medium flowingthrough the warming unit 10, for example, is external to the warmingunit 10 and is contained, for example, in the controller 30, as shown inFIG. 1. Consequently, the warming unit 10 is not susceptible toshorting, smoking, or catching fire, as may be caused, for example, byescaped medium contacting the control circuitry, as could have occurredin prior art devices in which the control circuitry was integral withthe warmer. As a result, in contrast to the prior art, the warming unit10 of the present invention provides improved patient and caregiversafety and reliability.

As best shown in FIG. 3, in one embodiment the second casing portion 120includes an outer concave surface 170 having a plurality ofcriss-crossing ribs 180. The ribs 180 of this embodiment form a gridpattern, for example, in the concave surface 170. The concave surface170 is able to conform to a portion of a patient's anatomy, for example,such as an arm or leg, and, thus position the warming unit 10 in astable manner when in use. The plurality of ribs 180 allow an air gap toexist between the patient and the warming unit 10 and thereby reduce thesurface area of the concave surface 170 in contact with the patient'sanatomy. As a result, the amount of heat transferred from the warmingunit 10 to the patient is reduced, increasing the patient's comfortlevel when the warming unit 10 is operating. In addition, the ribs 180generally increase rigidity of the unit 10.

As further shown in FIG. 3, the inner surface of the first casingportion 110 defines a first portion of a fluid conduit 190 extendingwithin the warming unit 10. According to one embodiment, this portion ofthe fluid conduit 190 defines a serpentine or meandering path,prolonging a time period (via increased path length of medium travel)during which a medium passing therethrough is in contact with, orlocated in close proximity to, the laminated heating assembly 50, versusa non-serpentine path.

As best shown in FIG. 2 and the cross-sectional views of FIGS. 4B and4C, in some embodiments, the laminated heating assembly 50 includes aplate or other substrate 200 sandwiched between first and secondinsulating sheets 210, 220, with a heating element 230 being located inor on the substrate 200. The surface of the laminated heating assembly50 facing the first casing portion 110 abuts the fluid conduit portion190 of the casing portion, so as to form an enclosed conduit uponassembly. Alternatively, a fluid conduit portion 290 is also formed onthe heating assembly 50 corresponding to the fluid conduit 190 of thecasing portion 110. The conduit of some embodiments of the presentinvention is formed with sizing and/or shaping of the cross-sectionalarea of the conduit such that air bubbles are unlikely to form in themedium to be conducted.

The reduced likelihood of bubble formation in the conduit results fromthe physics of bubbles. In general, the surface tension of a fluiddetermines the necessary wall tension for formation of bubbles, andbubbles generally form in spherical shapes due to the need for walltension to be minimized over the entire surface of the bubble. Thepressure difference between the air inside and the fluid outside of abubble depends on the surface tension of the fluid and the radius of thebubble, according to the following equation:

P _(i) −P _(o)=4T/r

where P_(i) is the pressure of air inside the bubble, P_(o) is thepressure of the fluid outside the bubble, T is the surface tension, andr is the radius of the bubble. See, e.g.,http://hyperphysics.phy-astrqsu.edu/hbase/surten2.html, as viewed onAug. 2, 2006, the entirety of which is incorporated herein by reference.Thus, generally, as r becomes very small (e.g., as must occur in a smallcross-sectional conduit), and as T is generally constant, the pressuredifference so as to form a bubble becomes increasingly larger, therebycorrespondingly reducing the likelihood that a bubble can form.

In embodiments of the present invention, the heating element 230 extendsadjacent or in close proximity to the fluid conduit 290, upon assembly.However, the shape of the heating element 230 is not so limited to theexample shown in FIG. 2, and it is within the scope of the presentinvention for the heating element 230 to form any shape within thewarming unit 10, such as a series of approximately parallel lineportions, a criss-crossing grid pattern, or a spiral pattern. Theheating element 230 may be formed from any suitable material, such as ametal, metal alloy, a ceramic, or any material that may provide heatingsuch as by passing an electrical current therethrough.

According to one embodiment, first and second sensors 60, 70 areattached to the laminated heating assembly 50. As shown in FIG. 2, thefirst sensor 60 is disposed within the fluid conduit 190 near the outlettube 100, although the first sensor 60 may be disposed anywhere withinor near the fluid conduit 190 (FIG. 3) to measure medium or other fluidtemperature at the point the sensor 60 is located. In one embodiment,the first sensor 60 is disposed within or near the outlet tube 90 (FIG.3) and within or near the fluid conduit 190 (FIG. 3), and measures theoutlet temperature of the medium (or other fluid) passing through thewarming unit 10, for example. The second sensor 70, as shown in FIG. 2,is disposed near an end of the warming unit 10, such as near the inlettube 90 (FIG. 3), although the second sensor 70 may be located at anylocation adjacent to or near the heating element 230, for example, tomeasure the temperature of the heating element 230. Examples of sensorsapplicable to the present invention include, but are not limited to,thermocouples, thermistors, resistor elements, and any other suitabledevice for measuring or otherwise determining temperature.

While FIG. 2 illustrates an embodiment of the warming unit 10 havingonly two sensors, it is within the scope of the present invention thatthe warming unit 10 include a single temperature sensor or that thewarming unit 10 include temperature sensors in excess of two. Moreover,the temperature measuring function may be performed by other methods andhardware than the sensors 60, 70, such as by measuring the power appliedto the heating element 230. Thus, the heating element 230 may be used toperform both a warming function and a temperature sensing function,permitting the elimination of a dedicated temperature measuring sensor.

It is also within the scope of the present invention that the warmingunit 10 include other features, such as a flowrate measurement deviceand/or medium leakage detection features. The flowrate measurementdevice measures a flowrate of a medium passing through the warming unit10 or the total amount of a medium delivered to a patient through thewarming unit 10 over a specified period of time, for example. Theleakage detection features detect the presence of leakage conditions,such as the presence of moisture outside the conduit path.

In one embodiment, circuit paths 240 for the first and second sensors60, 70 and the heating element 230 extend from the respective devices toa connector portion 250 of the laminated heating assembly 50. In oneembodiment, the circuit paths 240 are formed using printed circuit boardmanufacturing methods. Alternately, for example, the circuit paths 240comprise a plurality of wires or other couplings.

The exemplary warming unit 10 of FIG. 2 includes six circuit pathportions 240, wherein one pair of circuit paths 240 extend from each ofthe first and second sensor 60, 70, and a pair of circuit paths 240extend from the heating element 230. Each circuit path 240 terminates atthe connector portion 250.

A connector 40 engages the connector portion 250 to provide power to theheating element 230 and to transmit signals between the first and secondsensors 60, 70 and the controller 30. While the connector 40 isillustrated as mating with a six-pin connector portion 250, it is withinthe scope of the present invention for the connector 40 to beconnectable to any appropriate number of pins. For example, a warmingunit 10 with more devices (e.g., additional sensors or a flowratemeasurement device) may include an increased number of pins.Accordingly, a connector 40 with an increased number of pin connectionsmay be required. Conversely, a warming unit 10 with fewer devicesrequires fewer corresponding pins. In one embodiment, the connector 40is detachable from the warming unit 10, allowing the warming unit 10 tobe easily disconnected from the controller 30. Among other things, useof such a detachable connector provides flexibility in portability ofthe warming unit and allows the use of a variety of power sources (e.g.,any power source meeting the power requirements may be connected via theconnector portion 250, so long as suitable connection mechanism formating with the connector portion 250 is provided). Once detached, thewarming unit 10 may be discarded or otherwise removed, for example, anda new warming unit 10 may be attached to the connector 40. The warmingunit 10 may also be permanently connected to the controller 30 or powersupply 20, such as by soldered or otherwise permanently attachedcoupling, rather than via a detachable connector 40.

As further shown in FIGS. 2 and 3, the inlet tube 90 and the outlet tube100 are attached within respective openings in the casing portion 110 ofthe warming unit 10 and, for example, may be permanently attached. Anembodiment of the warming unit 10 in which the inlet and outlet tubes90, 100 are permanently attached significantly reduces or eliminatesrisk of leakage at the interface of the inlet and outlet tubes 90, 100with the casing portion 110 of the fluid warmer 10 relative to prior artdetachable tubes. In one embodiment, the inlet tube 90 comprisesflexible intravenous tubing. The inlet tube 90 and outlet tube 100 mayalso integrally or detachably include any intravenous tubing fittingsand/or related features, such as a male or female luer, a three-waystopcock, a Y-site connector (also referred to herein as “Y-fitting”), aslide thumb wheel, a slide pitch plate, a check valve, and/or aneedleless injection site luer.

A Y-fitting or three-way stopcock included with the input tube 90 isuseable, for example, for introducing a second medium that is also to bewarmed, since the second medium will pass through the warming unit 10with a first warmed medium prior to entering the patient's body.Conversely, a Y-fitting or three-way stopcock included with the outputtube 100 is usable for introducing a second medium, for which passagethrough the warming unit 10 is not desired. For example, oncology drugsfor which effectiveness is altered by heat may be introduced at aposition downstream from the warming unit 10 to prevent inappropriate orharmful warming from adversely affecting the drugs. Additionally, theinlet tube 90 and outlet tube 100 may also include features foracceptance of a needle, spike, or catheter, for example, particularlywithin or proximate to the outlet tube 100. It is within the scope ofthe invention to include any intravenous tubing fitting or other featureusable with standard intravenous tubing applications.

FIG. 4A is a perspective view of a central portion of the warming unit,in accordance with an embodiment of the present invention.

FIG. 5 is another perspective view of the warming unit of FIG. 4A.

An example embodiment of the warming unit including various types ofintravenous fittings is illustrated in FIG. 6.

FIG. 7 is a side view of a warming unit according to an embodiment ofthe present invention.

While there has been described what are at present considered to bepreferred embodiments of the present invention, it will be understoodthat various modifications may be made thereto. All such modificationsare considered to fall within the true spirit and scope of theinvention. Other modifications will be apparent to those skilled in theart.

1. A warming unit for warming a patient infusion medium comprising: aninlet tube; an outlet tube; a fluid conduit disposed between and incommunication with the inlet tube and the outlet tube; a heater disposedproximate to the fluid conduit for warming the patient infusion medium;and an outer casing sealably enclosing the fluid conduit and housing theheater, wherein at least a portion of the fluid conduit is defined by aninner surface of the outer casing.
 2. The warming unit according toclaim 1, wherein the inlet tube and the outlet tube are permanentlyattached to the outer casing.
 3. The warming unit according to claim 1,the heater comprising: a substrate; and a heating element disposed onthe substrate.
 4. The warming unit according to claim 3, wherein thefluid conduit forms a serpentine path; wherein the heating element formsa shape corresponding to the serpentine path of the fluid conduit; andwherein the shape of the heating element and the path of the fluidconduit generally align.
 5. The warming unit according to claim 1,further comprising: a connector that couples the warming unit to aseparate controller that is located externally to the outer casing ofthe warming unit.
 6. The warming unit according to claim 1, furthercomprising: a sensor for measuring a temperature of the patient infusionmedium passing through the warming unit.
 7. The warming unit accordingto claim 6, wherein the sensor is disposed within the fluid conduit. 8.The warming unit according to claim 1, wherein a portion of the fluidconduit is defined by the heater.
 9. The warming unit according to claim1, wherein a portion of the outer casing is contoured to conform to ananatomical shape of a patient.
 10. The warming unit according to claim9, wherein the contoured portion outer casing is configured to providean air gap between a portion of the outer casing and a patient.
 11. Thewarming unit according to claim 1, wherein the warming unit isdisposable.
 12. The warming unit according to claim 1, wherein the outercasing comprises: a first casing portion; and a second casing portion,wherein the first and second casing portions are permanently attachableto each other.
 13. The warming unit according to claim 12, furthercomprising: a seal disposed between the first and second casingportions.
 14. The warming unit according to claim 1, wherein the heatercomprises a laminated heating assembly, the assembly including: a firstinsulating sheet; a second insulating sheet; a substrate disposedbetween the first and second insulating sheets; a heating elementdisposed on the substrate, wherein a portion of the fluid conduit isdefined by the laminated heating assembly; a sensor disposed on thesubstrate; and a plurality of electrical circuit paths coupled to theheating element and the sensor.
 15. The warming unit according to claim14, wherein the plurality of circuit paths extend to the connector. 16.The warming unit according to claim 14, wherein the plurality of circuitpaths are formed on the substrate.
 17. The warming unit according toclaim 14, wherein the fluid conduit forms a serpentine path; wherein theheating element forms a shape corresponding to the serpentine path ofthe fluid conduit; and wherein the shape of the heating element and thepath of the fluid conduit generally align.
 18. A system for deliveringand warming a patient infusion medium comprising: a warming unit, thewarming unit including: an inlet tube; an outlet tube; a fluid conduitdisposed between and in communication with the inlet tube and the outlettube; a heating element disposed proximate to the fluid conduit forwarming the patient infusion medium, wherein a portion of the fluidconduit is defined by the heating element; and an outer casing enclosingthe fluid conduit and the heating member, wherein at least a portion ofthe fluid conduit is defined by an inner surface of the outer casing; acontroller provided outside the outer casing for controlling anoperation of the warming unit; and a power supply for providing power tothe warming unit.
 19. The system according to claim 18, furthercomprising: a reservoir connected to the warming unit.
 20. The systemaccording to claim 18, wherein the fluid conduit forms a serpentinepath; wherein the heating element forms a shape corresponding to theserpentine path of the fluid conduit; and wherein the shape of theheating element and the path of the fluid conduit generally align. 21.The system according to claim 18, the warming unit further comprising: aconnector portion for coupling the warming unit to the controller. 22.The system according to claim 18, further comprising: a fitting coupledto the outlet tube; wherein a second patient infusion medium isintroduced to the outlet tube via the fitting.
 23. The system accordingto claim 22, wherein the second patient infusion medium is introducedvia the fitting so as to avoid adverse heating effects on the secondpatient infusion media.
 24. The system according to claim 22, whereinthe second patient infusion medium includes an oncology drug.